Add access to dense_vector values (#71847)

Allow direct access to a dense_vector' values in script
through the following functions:

- getVectorValue – returns a vector's value as an array of floats
- getMagnitude – returns a vector's magnitude

Closes #51964
Backport for #71313

docs/reference/mapping/types/dense-vector.asciidoc

@@ -10,9 +10,8 @@ A `dense_vector` field stores dense vectors of float values.
 The maximum number of dimensions that can be in a vector should
 not exceed 2048. A `dense_vector` field is a single-valued field.
 
-These vectors can be used for <<vector-functions,document scoring>>.
-For example, a document score can represent a distance between
-a given query vector and the indexed document vector.
+`dense_vector` fields do not support querying, sorting or aggregating. They can
+only be accessed in scripts through the dedicated <<vector-functions,vector functions>>.
 
 You index a dense vector as an array of floats.
 
@@ -47,4 +46,4 @@ PUT my-index-000001/_doc/2
 
 --------------------------------------------------
 
-<1> dims—the number of dimensions in the vector, required parameter.
+<1> dims – the number of dimensions in the vector, required parameter.

docs/reference/vectors/vector-functions.asciidoc

@@ -10,6 +10,15 @@ to limit the number of matched documents with a `query` parameter.
 
 ====== `dense_vector` functions
 
+This is the list of available vector functions and vector access methods:
+
+1. `cosineSimilarity` – calculates cosine similarity
+2. `dotProduct` – calculates dot product
+3. `l1norm` – calculates L^1^ distance
+4. `l2norm` - calculates L^2^ distance
+5. `doc[<field>].vectorValue` – returns a vector's value as an array of floats
+6. `doc[<field>].magnitude` – returns a vector's magnitude
+
 Let's create an index with a `dense_vector` mapping and index a couple
 of documents into it.
 
@@ -198,6 +207,54 @@ You can check if a document has a value for the field `my_vector` by
 --------------------------------------------------
 // NOTCONSOLE
 
+The recommended way to access dense vectors is through `cosineSimilarity`,
+`dotProduct`, `l1norm` or `l2norm` functions. But for custom use cases,
+you can access dense vectors's values directly through the following functions:
+
+- `doc[<field>].vectorValue` – returns a vector's value as an array of floats
+
+- `doc[<field>].magnitude` – returns a vector's magnitude as a float
+(for vectors created prior to version 7.5 the magnitude is not stored.
+So this function calculates it anew every time it is called).
+
+For example, the script below implements a cosine similarity using these
+two functions:
+
+[source,console]
+--------------------------------------------------
+GET my-index-000001/_search
+{
+  "query": {
+    "script_score": {
+      "query" : {
+        "bool" : {
+          "filter" : {
+            "term" : {
+              "status" : "published"
+            }
+          }
+        }
+      },
+      "script": {
+        "source": """
+          float[] v = doc['my_dense_vector'].vectorValue;
+          float vm = doc['my_dense_vector'].magnitude;
+          float dotProduct = 0;
+          for (int i = 0; i < v.length; i++) {
+            dotProduct += v[i] * params.queryVector[i];
+          }
+          return dotProduct / (vm * (float) params.queryVectorMag);
+        """,
+        "params": {
+          "queryVector": [4, 3.4, -0.2],
+          "queryVectorMag": 5.25357
+        }
+      }
+    }
+  }
+}
+--------------------------------------------------
+
 ====== `sparse_vector` functions
 
 deprecated[7.6, The `sparse_vector` type is deprecated and will be removed in 8.0.]

server/src/main/java/org/elasticsearch/common/lucene/search/function/ScriptScoreFunction.java

@@ -14,7 +14,6 @@
 import org.elasticsearch.script.ExplainableScoreScript;
 import org.elasticsearch.script.ScoreScript;
 import org.elasticsearch.script.Script;
-import org.elasticsearch.Version;
 
 import java.io.IOException;
 import java.util.Objects;
@@ -42,15 +41,13 @@ public float score() {
 
     private final int shardId;
     private final String indexName;
-    private final Version indexVersion;
 
-    public ScriptScoreFunction(Script sScript, ScoreScript.LeafFactory script, String indexName, int shardId, Version indexVersion) {
+    public ScriptScoreFunction(Script sScript, ScoreScript.LeafFactory script, String indexName, int shardId) {
         super(CombineFunction.REPLACE);
         this.sScript = sScript;
         this.script = script;
         this.indexName = indexName;
         this.shardId = shardId;
-        this.indexVersion = indexVersion;
     }
 
     @Override
@@ -60,7 +57,6 @@ public LeafScoreFunction getLeafScoreFunction(LeafReaderContext ctx) throws IOEx
         leafScript.setScorer(scorer);
         leafScript._setIndexName(indexName);
         leafScript._setShard(shardId);
-        leafScript._setIndexVersion(indexVersion);
         return new LeafScoreFunction() {
             @Override
             public double score(int docId, float subQueryScore) throws IOException {

server/src/main/java/org/elasticsearch/common/lucene/search/function/ScriptScoreQuery.java

@@ -146,7 +146,6 @@ private ScoreScript makeScoreScript(LeafReaderContext context) throws IOExceptio
                 final ScoreScript scoreScript = scriptBuilder.newInstance(context);
                 scoreScript._setIndexName(indexName);
                 scoreScript._setShard(shardId);
-                scoreScript._setIndexVersion(indexVersion);
                 return scoreScript;
             }
 

server/src/main/java/org/elasticsearch/index/query/functionscore/ScriptScoreFunctionBuilder.java

@@ -83,8 +83,7 @@ protected ScoreFunction doToFunction(SearchExecutionContext context) {
         try {
             ScoreScript.Factory factory = context.compile(script, ScoreScript.CONTEXT);
             ScoreScript.LeafFactory searchScript = factory.newFactory(script.getParams(), context.lookup());
-            return new ScriptScoreFunction(script, searchScript,
-                context.index().getName(), context.getShardId(), context.indexVersionCreated());
+            return new ScriptScoreFunction(script, searchScript, context.index().getName(), context.getShardId());
         } catch (Exception e) {
             throw new QueryShardException(context, "script_score: the script could not be loaded", e);
         }

server/src/main/java/org/elasticsearch/script/ScoreScript.java

@@ -10,7 +10,6 @@
 import org.apache.lucene.index.LeafReaderContext;
 import org.apache.lucene.search.Explanation;
 import org.apache.lucene.search.Scorable;
-import org.elasticsearch.Version;
 import org.elasticsearch.common.logging.DeprecationCategory;
 import org.elasticsearch.common.logging.DeprecationLogger;
 import org.elasticsearch.index.fielddata.ScriptDocValues;
@@ -85,7 +84,6 @@ public Explanation get(double score, Explanation subQueryExplanation) {
     private int docId;
     private int shardId = -1;
     private String indexName = null;
-    private Version indexVersion = null;
 
     public ScoreScript(Map<String, Object> params, SearchLookup lookup, LeafReaderContext leafContext) {
         // null check needed b/c of expression engine subclass
@@ -185,19 +183,6 @@ public String _getIndex() {
         }
     }
 
-    /**
-     *  Starting a name with underscore, so that the user cannot access this function directly through a script
-     *  It is only used within predefined painless functions.
-     * @return index version or throws an exception if the index version is not set up for this script instance
-     */
-    public Version _getIndexVersion() {
-        if (indexVersion != null) {
-            return indexVersion;
-        } else {
-            throw new IllegalArgumentException("index version can not be looked up!");
-        }
-    }
-
     /**
      *  Starting a name with underscore, so that the user cannot access this function directly through a script
      */
@@ -212,13 +197,6 @@ public void _setIndexName(String indexName) {
         this.indexName = indexName;
     }
 
-    /**
-     *  Starting a name with underscore, so that the user cannot access this function directly through a script
-     */
-    public void _setIndexVersion(Version indexVersion) {
-        this.indexVersion = indexVersion;
-    }
-
 
     /** A factory to construct {@link ScoreScript} instances. */
     public interface LeafFactory {

x-pack/plugin/src/yamlRestTest/resources/rest-api-spec/test/vectors/30_dense_vector_script_access.yml

@@ -0,0 +1,65 @@
+---
+"Access to values of dense_vector in script":
+  - skip:
+      version: " - 7.12.99"
+      reason: "Access to values of dense_vector in script was added in 7.13"
+  - do:
+      indices.create:
+        index: test-index
+        body:
+          mappings:
+            properties:
+              v:
+                type: dense_vector
+                dims: 3
+
+  - do:
+      bulk:
+        index: test-index
+        refresh: true
+        body:
+          - '{"index": {"_id": "1"}}'
+          - '{"v": [1, 1, 1]}'
+          - '{"index": {"_id": "2"}}'
+          - '{"v": [1, 1, 2]}'
+          - '{"index": {"_id": "3"}}'
+          - '{"v": [1, 1, 3]}'
+          - '{"index": {"_id": "missing_vector"}}'
+          - '{}'
+
+  # vector functions in loop – return the index of the closest parameter vector based on cosine similarity
+  - do:
+      search:
+        body:
+          query:
+            script_score:
+              query: { "exists": { "field": "v" } }
+              script:
+                source: |
+                  float[] v = doc['v'].vectorValue;
+                  float vm = doc['v'].magnitude;
+
+                  int closestPv = 0;
+                  float maxCosSim = -1;
+                  for (int i = 0; i < params.pvs.length; i++) {
+                    float dotProduct = 0;
+                    for (int j = 0; j < v.length; j++) {
+                      dotProduct += v[j] * params.pvs[i][j];
+                    }
+                    float cosSim = dotProduct / (vm * (float) params.pvs_magnts[i]);
+                    if (maxCosSim < cosSim) {
+                      maxCosSim = cosSim;
+                      closestPv = i;
+                    }
+                  }
+                  closestPv;
+                params:
+                  pvs: [ [ 1, 1, 1 ], [ 1, 1, 2 ], [ 1, 1, 3 ] ]
+                  pvs_magnts: [1.7320, 2.4495, 3.3166]
+
+  - match: { hits.hits.0._id: "3" }
+  - match: { hits.hits.0._score: 2 }
+  - match: { hits.hits.1._id: "2" }
+  - match: { hits.hits.1._score: 1 }
+  - match: { hits.hits.2._id: "1" }
+  - match: { hits.hits.2._score: 0 }

x-pack/plugin/vectors/src/main/java/org/elasticsearch/xpack/vectors/mapper/DenseVectorFieldMapper.java

@@ -83,7 +83,7 @@ protected List<Parameter<?>> getParameters() {
         public DenseVectorFieldMapper build(ContentPath contentPath) {
             return new DenseVectorFieldMapper(
                 name,
-                new DenseVectorFieldType(buildFullName(contentPath), dims.getValue(), meta.getValue()),
+                new DenseVectorFieldType(buildFullName(contentPath), indexVersionCreated, dims.getValue(), meta.getValue()),
                 dims.getValue(),
                 indexVersionCreated,
                 multiFieldsBuilder.build(this, contentPath),
@@ -95,10 +95,12 @@ public DenseVectorFieldMapper build(ContentPath contentPath) {
 
     public static final class DenseVectorFieldType extends MappedFieldType {
         private final int dims;
+        private final Version indexVersionCreated;
 
-        public DenseVectorFieldType(String name, int dims, Map<String, String> meta) {
+        public DenseVectorFieldType(String name, Version indexVersionCreated, int dims, Map<String, String> meta) {
             super(name, false, false, true, TextSearchInfo.NONE, meta);
             this.dims = dims;
+            this.indexVersionCreated = indexVersionCreated;
         }
 
         int dims() {
@@ -125,7 +127,7 @@ protected Object parseSourceValue(Object value) {
 
         @Override
         public DocValueFormat docValueFormat(String format, ZoneId timeZone) {
-            throw new UnsupportedOperationException(
+            throw new IllegalArgumentException(
                 "Field [" + name() + "] of type [" + typeName() + "] doesn't support docvalue_fields or aggregations");
         }
 
@@ -136,7 +138,7 @@ public boolean isAggregatable() {
 
         @Override
         public IndexFieldData.Builder fielddataBuilder(String fullyQualifiedIndexName, Supplier<SearchLookup> searchLookup) {
-            return new VectorIndexFieldData.Builder(name(), true, CoreValuesSourceType.KEYWORD);
+            return new VectorIndexFieldData.Builder(name(), true, CoreValuesSourceType.KEYWORD, indexVersionCreated, dims);
         }
 
         @Override

x-pack/plugin/vectors/src/main/java/org/elasticsearch/xpack/vectors/mapper/SparseVectorFieldMapper.java

@@ -71,7 +71,7 @@ protected List<Parameter<?>> getParameters() {
         @Override
         public SparseVectorFieldMapper build(ContentPath contentPath) {
             return new SparseVectorFieldMapper(
-                    name, new SparseVectorFieldType(buildFullName(contentPath), meta.getValue()),
+                    name, new SparseVectorFieldType(buildFullName(contentPath), indexCreatedVersion, meta.getValue()),
                     multiFieldsBuilder.build(this, contentPath), copyTo.build(), indexCreatedVersion);
         }
     }
@@ -83,8 +83,10 @@ name, new SparseVectorFieldType(buildFullName(contentPath), meta.getValue()),
 
     public static final class SparseVectorFieldType extends MappedFieldType {
 
-        public SparseVectorFieldType(String name, Map<String, String> meta) {
+        private final Version indexVersionCreated;
+        public SparseVectorFieldType(String name, Version indexVersionCreated, Map<String, String> meta) {
             super(name, false, false, true, TextSearchInfo.NONE, meta);
+            this.indexVersionCreated = indexVersionCreated;
         }
 
         @Override
@@ -94,7 +96,7 @@ public String typeName() {
 
         @Override
         public DocValueFormat docValueFormat(String format, ZoneId timeZone) {
-            throw new UnsupportedOperationException(
+            throw new IllegalArgumentException(
                 "Field [" + name() + "] of type [" + typeName() + "] doesn't support docvalue_fields or aggregations");
         }
 
@@ -118,7 +120,7 @@ public Query existsQuery(SearchExecutionContext context) {
 
         @Override
         public IndexFieldData.Builder fielddataBuilder(String fullyQualifiedIndexName, Supplier<SearchLookup> searchLookup) {
-            return new VectorIndexFieldData.Builder(name(), false, CoreValuesSourceType.KEYWORD);
+            return new VectorIndexFieldData.Builder(name(), false, CoreValuesSourceType.KEYWORD, indexVersionCreated, -1);
         }
 
         @Override

x-pack/plugin/vectors/src/main/java/org/elasticsearch/xpack/vectors/mapper/VectorEncoderDecoder.java

@@ -14,7 +14,6 @@
 
 import java.nio.ByteBuffer;
 
-// static utility functions for encoding and decoding dense_vector and sparse_vector fields
 public final class VectorEncoderDecoder {
     static final byte INT_BYTES = 4;
     static final byte SHORT_BYTES = 2;
@@ -168,9 +167,51 @@ public static int denseVectorLength(Version indexVersion, BytesRef vectorBR) {
      * NOTE: this function can only be called on vectors from an index version greater than or
      * equal to 7.5.0, since vectors created prior to that do not store the magnitude.
      */
-    public static float decodeVectorMagnitude(Version indexVersion, BytesRef vectorBR) {
+    public static float decodeMagnitude(Version indexVersion, BytesRef vectorBR) {
         assert indexVersion.onOrAfter(Version.V_7_5_0);
         ByteBuffer byteBuffer = ByteBuffer.wrap(vectorBR.bytes, vectorBR.offset, vectorBR.length);
-        return byteBuffer.getFloat(vectorBR.offset + vectorBR.length - 4);
+        return byteBuffer.getFloat(vectorBR.offset + vectorBR.length - INT_BYTES);
     }
+
+    /**
+     * Calculates vector magnitude
+     */
+    private static float calculateMagnitude(Version indexVersion, BytesRef vectorBR) {
+        final int length = denseVectorLength(indexVersion, vectorBR);
+        ByteBuffer byteBuffer = ByteBuffer.wrap(vectorBR.bytes, vectorBR.offset, vectorBR.length);
+        double magnitude = 0.0f;
+        for (int i = 0; i < length; i++) {
+            float value = byteBuffer.getFloat();
+            magnitude += value * value;
+        }
+        magnitude = Math.sqrt(magnitude);
+        return (float) magnitude;
+    }
+
+    public static float getMagnitude(Version indexVersion, BytesRef vectorBR) {
+        if (vectorBR == null) {
+            throw new IllegalArgumentException("A document doesn't have a value for a vector field!");
+        }
+        if (indexVersion.onOrAfter(Version.V_7_5_0)) {
+            return decodeMagnitude(indexVersion, vectorBR);
+        } else {
+            return calculateMagnitude(indexVersion, vectorBR);
+        }
+    }
+
+    /**
+     * Decodes a BytesRef into the provided array of floats
+     * @param vectorBR - dense vector encoded in BytesRef
+     * @param vector - array of floats where the decoded vector should be stored
+     */
+    public static void decodeDenseVector(BytesRef vectorBR, float[] vector) {
+        if (vectorBR == null) {
+            throw new IllegalArgumentException("A document doesn't have a value for a vector field!");
+        }
+        ByteBuffer byteBuffer = ByteBuffer.wrap(vectorBR.bytes, vectorBR.offset, vectorBR.length);
+        for (int dim = 0; dim < vector.length; dim++) {
+            vector[dim] = byteBuffer.getFloat();
+        }
+    }
+
 }